Re: [PATCH] x86/viridian: EOI MSR should always happen in affected vCPU context

[Paul Durrant]

On 01/04/2021 11:22, Roger Pau Monne wrote:

The HV_X64_MSR_EOI wrmsr should always happen with the target vCPU
as current, as there's no support for EOI'ing interrupts on a remote
vCPU.
While there also turn the unconditional assert at the top of the
function into an error on non-debug builds.

No functional change intended.

Requested-by: Jan Beulich <jbeul...@suse.com>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>

Reviewed-by: Paul Durrant <p...@xen.org>

---
  xen/arch/x86/hvm/viridian/synic.c | 11 ++++++++++-
  1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/viridian/synic.c 
b/xen/arch/x86/hvm/viridian/synic.c
index 22e2df27e5d..e18538c60a6 100644
--- a/xen/arch/x86/hvm/viridian/synic.c
+++ b/xen/arch/x86/hvm/viridian/synic.c
@@ -79,11 +79,20 @@ int viridian_synic_wrmsr(struct vcpu *v, uint32_t idx, 
uint64_t val)
      struct viridian_vcpu *vv = v->arch.hvm.viridian;
      struct domain *d = v->domain;

- ASSERT(v == current || !v->is_running);

+    if ( v != current && v->is_running )
+    {
+        ASSERT_UNREACHABLE();
+        return X86EMUL_EXCEPTION;
+    }

switch ( idx )

      {
      case HV_X64_MSR_EOI:
+        if ( v != current )
+        {
+            ASSERT_UNREACHABLE();
+            return X86EMUL_EXCEPTION;
+        }
          vlapic_EOI_set(vcpu_vlapic(v));
          break;